The present invention concerns improvements in the device according to the above mentioned U.S. Pat. No. 3,887,138.
As has been mentioned in my said Patent, the two elements, one extending within the other, are manufactured by an extrusion process and are fused together by heat treatment. Thus a continuous conduit is obtained which serves a twofold purpose -- it is the feed conduit conducting a flow of water, and at the same time serves as the means for emitting a trickle or drip-emission of irrigation water.
In practice the grooving of the hose conduit is performed by two oppositely disposed jaws which are positioned at the exit of the extruded hose from the extrusion tool, and which press from both sides against the still mouldable mass of the emerging hose, imparting to it the desired grooving.